The work described here is designed to characterize a model system for rhodopsin in the rod disc membrane which is amenable to detailed physical-chemical studies. It is our ultimate goal to fully understand the mechanism of action of rhodopsin/opsin in molecular terms. When these studies are complete we will be in a position to understand the role of rhodopsin in visual excitation and, further, have a precise understanding of integral membrane proteins and at least some of the factors that control their action. GOALS FOR THE COMING YEAR: 1. Complete the exchange to sodium cholate for TETAB and compare the kinetics of regeneration of lipid free rhodopsin to those with a normal lipid composition. If differences exist, then we can add back specific lipids to determine their role. 2. To obtain electron micrographs of 2 and 20 mg/ml cholate solubilized rhodopsin and determine the physical states of these complexes. 3. To obtain sufficient quantities of rhodopsin solubilized from rat and rabbit retinas to determine their stability, regeneration kinetics and suitability for structural studies.